In recent years, use of content distribution services such as video distribution services and music distribution services has become widespread. Among these services, there exist download-based distribution services in which entire data for a playback is first downloaded into a playback terminal before performing the playback, and streaming-based distribution services in which a playback is performed simultaneously with downloading the data.
Among these services, compared to the download-based distribution services, the streaming-based distribution service generally takes a shorter time to make a video ready to be viewed and listened to, and hence, a large number of users use streaming-based distribution services. Also, progress of the adaptive bitrate technology that dynamically changes the image quality depending on the communication environment makes streaming-based distribution services widely used in mobile environments. Meanwhile, in a streaming-based distribution service, since the service can be used easily, it is quite often the case that the user suspends viewing. In such a case, since data that has been accumulated in a buffer until the viewing is suspended is discarded without being viewed, the traffic turns out to be useless.
Thereupon, what-is-called “pacing technologies” have been proposed that control the buffered amount of data so as not to be accumulated excessively within a range where playback stalling does not occur. Pacing technologies that have been proposed include a method that sets two thresholds (denoted as Tha and Thb), to stop buffering more if the buffered amount reaches Tha, and to resume buffering if the buffered amount decreases to Thb; and a method that predicts a stochastic spread of the throughput, to prevent playback stalling (Non-patent document 1).